package com.edu.base.common;

import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.SecureRandom;

import org.apache.commons.lang3.Validate;

import com.edu.base.common.utils.Exceptions;

public class Digests {
	private static final String SHA1 = "SHA-1";
	private static final String MD5 = "MD5";
	private static SecureRandom random = new SecureRandom();

	public static byte[] md5(byte[] input) {
		return digest(input, "MD5", null, 1);
	}

	public static byte[] md5(byte[] input, int iterations) {
		return digest(input, "MD5", null, iterations);
	}

	public static byte[] sha1(byte[] input) {
		return digest(input, "SHA-1", null, 1);
	}

	public static byte[] sha1(byte[] input, byte[] salt) {
		return digest(input, "SHA-1", salt, 1);
	}

	public static byte[] sha1(byte[] input, byte[] salt, int iterations) {
		return digest(input, "SHA-1", salt, iterations);
	}

	private static byte[] digest(byte[] input, String algorithm, byte[] salt, int iterations) {
		try {
			MessageDigest digest = MessageDigest.getInstance(algorithm);
			if (salt != null) {
				digest.update(salt);
			}
			byte[] result = digest.digest(input);
			for (int i = 1; i < iterations; i++) {
				digest.reset();
				result = digest.digest(result);
			}
			return result;
		} catch (GeneralSecurityException e) {
			throw Exceptions.unchecked(e);
		}
	}

	public static byte[] generateSalt(int numBytes) {
		Validate.isTrue(numBytes > 0, "numBytes argument must be a positive integer (1 or larger)", numBytes);

		byte[] bytes = new byte[numBytes];
		random.nextBytes(bytes);
		return bytes;
	}

	public static byte[] md5(InputStream input) throws IOException {
		return digest(input, "MD5");
	}

	public static byte[] sha1(InputStream input) throws IOException {
		return digest(input, "SHA-1");
	}

	private static byte[] digest(InputStream input, String algorithm) throws IOException {
		try {
			MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
			int bufferLength = 8192;
			byte[] buffer = new byte[bufferLength];
			int read = input.read(buffer, 0, bufferLength);
			while (read > -1) {
				messageDigest.update(buffer, 0, read);
				read = input.read(buffer, 0, bufferLength);
			}
			return messageDigest.digest();
		} catch (GeneralSecurityException e) {
			throw Exceptions.unchecked(e);
		}
	}

	public static String string2MD5(String inStr) {
		MessageDigest md5 = null;
		try {
			md5 = MessageDigest.getInstance("MD5");
		} catch (Exception e) {
			System.out.println(e.toString());
			e.printStackTrace();
			return "";
		}
		char[] charArray = inStr.toCharArray();
		byte[] byteArray = new byte[charArray.length];
		for (int i = 0; i < charArray.length; i++) {
			byteArray[i] = ((byte) charArray[i]);
		}
		byte[] md5Bytes = md5.digest(byteArray);
		StringBuffer hexValue = new StringBuffer();
		for (int i = 0; i < md5Bytes.length; i++) {
			int val = md5Bytes[i] & 0xFF;
			if (val < 16) {
				hexValue.append("0");
			}
			hexValue.append(Integer.toHexString(val));
		}
		return hexValue.toString();
	}
}
